In packaging of a semiconductor operating at very high frequencies such as millimeter waves (hereinafter, referred to as a millimeter wave semiconductor chip), how to realize an interface for an RF signal is an important issue.
In other words, even though an electrode drawing structure or a soldered structure employed in packaging of a normal semiconductor integrated circuit is applied to packaging of the millimeter wave semiconductor chip, desired characteristics may not be stably obtained due to significant degradation of a signal intensity of the RF signal.
In an electric/electronic apparatus using millimeter waves, a waveguide tube is often used as an RF interface with respect to passive components such as filters and antennas which require strict performances.
Accordingly, when packaging the millimeter wave semiconductor chip, a configuration of the RF interface that is similar to the waveguide tube is considered to be effective.
When the wave guide tube is employed as the RF interface of the millimeter wave semiconductor chip, the RF interface is assumed to be connected to a microstrip line, a coplanar line, or the like, and thus provision of a connection mechanism for the microstrip line portion and the coplanar line with respect to the waveguide tube may be required in the package.
When considering an application for millimeter waves such as a fixed communication equipment for frequency bands referred to as a V-band (60 GHz) and an E-band (70/80 GHz), a broad frequency band may be used, and thus high-speed communication is advantageously achieved. Therefore, when realizing the millimeter wave semiconductor apparatus, it is desired to provide the RF interface with broadband frequency characteristics.
In order to do so, realization of broadband characteristics without loss is required in connection between the microstrip line portion and the waveguide tube and, in addition, these members are required to be compact enough to be accommodated in the package and to be manufactured at low costs.
FIG. 13 is a drawing illustrating an example of a connection between a microstrip line portion 101 and a waveguide tube 102 on a ceramic substrate.
In this connection structure, a distal end (probe) 104 of the microstrip line portion 101 is inserted into the waveguide tube 102 in an open-state.
One of surfaces of the waveguide tube 102 corresponds to a short-circuit surface 103, and transmission characteristics are determined depending on a shape of the probe 104 and dimensions such as a distance between the probe 104 and the short-circuit surface 103.
Therefore, when manufacture with high degree of accuracy in dimension or the like is achieved, comparatively broadband characteristics are achieved. However, it is difficult to assemble such a structure into the package.
In JP 2001-85912 A (i.e designated as PTL1 below), a waveguide as illustrated in FIG. 14 is proposed. The waveguide described above has a configuration in which a microstrip line 110 formed on a printed substrate 113 is coupled to a slot 111 formed on a ground surface side of the microstrip line 110, and the slot 111 and a waveguide tube 112 are connected.
A technology disclosed in PTL2 (listed below) is also one of technologies in the related art.